The Cycle of Infection
A cycle of infection is also referred to as the chain of infection or chain of events consisting of six links of the infectious process in a logical sequence. The process can only take place if all the six links in the chain or cycle are intact. Therefore, any attempt to break the cycle at any given point can stop the spread of the infection. The cycle consists of six distinct links, including infectious agent, reservoir, the Portal of exit, mode of transmission, the Portal of entry, and the susceptible host.
The infectious agent is the pathogen causing the disease. Examples of the pathogens include viruses, bacteria, parasites, or fungi.
The reservoir is the host or the habitat in which the pathogen can live, grow, and multiply. These may include humans, animals, the environment, insects, medical equipment, water, and soil. Breaking the cycle at this stage would require cleaning, disinfection, pest control, and infection prevention policies.
The Portal of exit is the way or the path by which the pathogen leaves the reservoir. This can be through broken skin, mucous membranes, respiratory tract through coughing and sneezing, and aerosols. Breaking the cycle would require personal protective equipment (PPEs), respiratory etiquette, hand hygiene, waste disposal, safe handling of sharps, and the wearing of masks.
Mode of transmission, which is the way through which the infectious agents can be passed on to another party. This can be through direct or indirect contact, inhalation, or ingestion. Breaking the cycle at this stage would require isolation, personal protective equipment, food safety, hand hygiene, wearing a mask, sterilization, disinfection, and cleaning.
Portal of entry, which is the path the pathogen gets into the new host. This can be through the respiratory tract, wounds, mucous membranes, and catheters, and tubes. Breaking the cycle requires hand hygiene, first aid, and personal protective equipment, removal of catheters and tubes as well as personal hygiene.
The susceptible host is the person who is next exposed to the pathogen. This includes those who are receiving healthcare, or immunocompromised, or those having invasive medical devices. Breaking the chain would require immunizations, patient education, health insurance, treatment of the existing disease.